Linearized electronic fuel injection system

ABSTRACT

In synchronization with the speed of an internal combustion engine, a control voltage having a substantially constant amplitude is applied across an inductor to develop through the inductor a control current having a linearly varying magnitude. The inductance of the inductor is determined as a linear function of at least one engine operating parameter thereby to define the constant rate of change in the magnitude of the control current. Fuel is applied to the engine in an amount directly related to the rate of change in the magnitude of the control current so that the total quantity of fuel delivered to the engine is linearly related to the engine operating parameter.

United States Patent McGavic I Nov. 27, 1973 {22] Filed:

[ LINEARIZED ELECTRONIC FUEL INJECTION SYSTEM [75] Inventor: John P.McGavic, Lake Park, Fla.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

Oct. 2], 1971 [21] Appl. No.: 191,183

[52] US. Cl. 123/32 EA, 123/119 R [51] Int. C1. F02d'5/02, F0211] 51/00[58] Field Of Search 123/32 AB, 32 EA, 123/1 19 R [56] References CitedUNITED STATES PATENTS 3,203,410 8/1965 SCl'lOll 123/32 EA 3,338,2218/1967 SChOll 123/32 EA 3,448,728 6/1969 SChOll 123/32 EA 3,583,3746/1971 SChOll 123/32 EA Primary ExaminerLaurence M. Goodridge AssistantExaminerCort Flint Attorney-E. E. Christen et al.

[5 7 ABSTRACT In synchronization with the speed of an internalcombustion engine, a control voltage having a substantially constantamplitude is applied across an inductor to develop through the inductora control current having a linearly varying magnitude. The inductance ofthe inductor is determined as a linear function of at least one engineoperating parameter thereby to define the constant rate of change in themagnitude of the control current. Fuel is applied to the engine in anamount directly related to the rate of change in the magnitude of thecontrol current so that the total quantity of fuel delivered to theengine is linearly related to the engine operating parameter.

6 Claims, 2 Drawing Figures IGNITION I CIRCUIT PRESSURE SENSOR l l/J l,-//6' a, I

INJECTOR CDISEIUEIT 9/ Patented Nov. 27, 1973 3.774580 2 Sheets-Sheet 1PRESSURE SENSOR I id l ,//6' 87 l INJECTOR DRIVE ATTORNEY 2 Sheets-SheetF:

INVENTOR.

ATTORNEY LINEARIZED ELECTRONIC FUEL INJECTION SYSTEM This inventionrelates to a linearized electronic fuel injection system for an internalcombustion engine.

More particularly, the invention relates to an electronic fuel injectionsystem in which the total quantity of fuel delivered to the engine is alinear function of at least one engine operating parameter.

According to one aspect of the invention, a control voltage having asubstantially constant amplitude is applied in synchronization with thespeed of the engine across an inductor having an inductance which isdetermined as a linear function of at least one engine operatingparameter. As a result, a control current is developed through theinductor having a magnitude which linearly varies at a constant rate ofchange proportional to the engine operating parameter. Fuel is appliedto the engine in an amount determined by the rate of change in themagnitude of the control current so that the total quantity of fueldelivered to the engine is linearly related to the engine operatingparameter.

In another aspect of the invention, the control voltage is appliedacross the inductor by a transistor which is connected in anemitter-follower configuration between the inductor and at least oneresistor. Consequently, the control current developed through theinductor is also drawn through the resistor to generate a controlvoltage across the resistor having a magnitude which linearly variesfrom a peak level to a reference level at a constant rate of changedefined by the constant rate of change in the magnitude of the controlcurrent. The amount of fuel applied to the engine is determined indirect relation to the time period defined between the departure of thecontrol voltage from the peak level and the arrival of the controlvoltage at the reference level so that fuel is metered to the engine ata linear function of the engine operating parameter.

These and other aspects and advantages of the invention may be bestunderstood by reference to the following detail description of apreferred embodiment when considered in conjunction with theaccompanying drawing.

In the drawing:

FIG. 1 is a schematic diagram of an electronic fuel injection systemincorporating the principles of the invention.

FIG. 2 is a graphic diagram of several waveforms useful in explainingthe operation of the electronic fuel injection system illustrated inFIG. 1.

Referring to FIG. 1, an internal combustion engine for an automotivevehicle includes a combustion chamber or cylinder 12. A piston 14 ismounted for reciprocation within the cylinder 12. A crankshaft 16 issupported for rotation within the engine 10. A connecting rod 18 ispivotally connected between the piston 14 and the crankshaft 16 forrotating the crankshaft within the engine 10 when the piston 14 isreciprocated within the cylinder 12.

An intake manifold 20 is connected with the cylinder 12 through anintake port 22. An exhaust manifold 24 i is connected with the cylinder12 through an exhaust port 26. An intake valve 28 is slidably mountedwithin the top of the cylinder 12 in cooperation with the intake port 22for regulating the entry of combustion ingredients into the cylinderl2.from the intake manifold 20. A spark plug 30 is mounted in the top ofthe cylinder 12 for igniting the combustion ingredients within thecylinder 12 when the spark plug 30 is-energized. An exhaust valve 32 isslidably mounted in the top of the cylinder 12 in cooperation with theexhaust port 26 for regulating the exit of combustion products from thecylinder 12 into the exhaust manifold 24. The intake valve 28 and theexhaust valve 32 are driven through a suitable linkage 34 whichconventionally includes rocker arms, lifters and camshaft.

An electrical power source is provided by the vehicle batter 36. Anignition switch 38 connects the battery 36 between a power line 40 and aground line 42. When the ignition switch 38 is closed, the battery 36applies a supply voltage to the power line 40. A conventional ignitioncircuit 44 is electrically connected to the power line 40 and ismechanically connected with the crankshaft 16 of the engine 10. Further,the ignition circuit 44 is connected through a spark cable 46 to thespark plug 30. In a conventional manner, the ignition circuit 44energizes the spark plug 30 in synchronization with the rotation of thecrankshaft 16 of the engine 10. Hence, the ignition circuit 44 combineswith the ignition switch 38 and the spark plug 30 to form an ignitionsystem.

A fuel injector .48 includes a housing 50 having a fixed meteringorifice 52. A plunger 54 is supported within the housing 50 forreciprocation between a fully opened position and a fully closedposition. In the fully opened position, the forward end of the plunger54 is opened away from the orifice 52. In the fully closed position, theforward end of the plunger 54 is closed against the orifice 52. A biasspring 56 is seated between the rearward end of the plunger 54 and thehousing 50 for normally maintaining the plunger 54 in the fully closedposition. A solenoid or winding 58 is electromagnetically coupled withplunger 54 for driving the plunger 54 to the fully opened positionagainst the action of the bias spring 56 when the winding 58 isenergized. The bias spring 56 drives the plunger 54 to the fully closedposition when the winding 58 is deenergized. The fuel injector 48 ismounted on the intake manifold20 at a constant flow rate through themetering orifice 52 when the plunger 54 is in the fully opened position.Notwithstanding the illustrated structure, it is to be noted that thefuel injector 48 may be provided by virtually any suitable constant flowrate valve.

A fuel pump 60 is connected to the fuel injector 48 by a conduit 62 andto the vehicle fuel tank 64 by a conduit 66 for pumping fuel from thefuel tank 64 to the fuel injector 48. Preferably, the fuel pump 60 isconnected to'the power line 40 to be electrically driven from thevehicle battery 36. Alternatively, the fuel pump 60 could be connectedto the crankshaft 16 to be mechanically driven from the engine 10. Apressure regulator 68 is connected to the conduit 62 by a conduit 70 andis connected to the fuel tank 64 by a conduit 72 for defining thepressure of the fuel applied to the fuel injector 48. Thus, the fuelinjector 48 combines with the fuel tank 64, the fuel pump 60 and theprestween the accelerator pedal 78 and the reference surface. As theaccelerator pedal 78 is depressed, the throttle valve 74 is moved to amore opened position to increase the flow of air into the intakemanifold 20. Conversely, as the accelerator pedal 78 is released, thethrottle valve 74 is moved to a less opened position to decrease theflow of air into the intake manifold 20.

In operation, fuel and air are combined within the intake manifold 20 toform an air/fuel mixture. The fuel is injected into the intake manifold20 at a constant flow rate by the fuel injector 48 in response toenergization. The precise amount of fuel deposited within the intakemanifold 20 is regulated by a fuel supply control system which will bedescribed later. The air enters the intake manifold 20 from the airintake system (not shown) which conventionally includes an air filter.The precise amount of air admitted into the intake manifold 20 isdetermined by the position of the throttle valve 74. As previouslydescribed, the position of the accelerator pedal 78 controls theposition of th throttle valve 74.

As the piston 14 initially moves downward within the cylinder 12 on theintake stroke, the intake valve 28 is opened away from the intake port22 and the exhaust valve 32 is closed against the exhaust port 26.Accordingly, combustion ingredients in the form of the air/fuel mixturewithin the intake manifold 20 are drawn by negative pressure through theintake port 22 into the cylinder 12. As the piston 14 subsequently movesupward within the cylinder 12 on the compression stroke, the intakevalve 28 is closed against the intake port 22 so that the air/fuelmixture is compressed between the top of the piston 14 and the top ofthe cylinder 12. When the piston 14 reaches the end of its upward travelon the compression stroke, the spark plug 30 is energized by theignition circuit 44 to ignite the air/fuel mixture. The ignition of theair/fuel mixture starts a combustion reaction which drives the piston 14downward within the cylinder 12 on the power stroke. As the piston 14moves upward within the cylinder 12 on the exhaust stroke, the exhaustvalve 32 is opened away from the exhaust port 26. As a result, thecombustion products in the form of various exhaust gases are pushed bypositive pressure out of the cylinder 12 through the exhaust port 26into the exhaust manifold 24. The exhaust gases pass out of the exhaustmanifold 24 into the exhaust system (not shown) which conventionallyincludes a muffler and an exhaust pipe.

Although the structure and operation of only a single combustion chamberor cylinder 12 has been described, it will be readily appreciated thatthe illustrated internal combustion engine may include additionalcylinders 12 as desired. Similarly, additional fuel injectors 48 may beprovided as required. However, as long as the fuel injectors 48 aremounted on the intake manifold 20, the number of additional fuelinjectors 48 need not necessarily bear any fixed relation to the numberof additional cylinders 12. Alternately, the fuel injector 48 may bedirectly mounted on the cylinder 12 so as to inject fuel directly intothe cylinder 12. In such instance, the number of additional fuelinjectors 48 would necessarily equal the number of additional cylinders12. At this point, it is to be understood that the illustrated internalcombustion engine 10, together with all of its associated equipment, isshown only to facilitate a more complete understanding of the inventiveelectronic control system.

A timing pulse generator is connected with the crankshaft 16 fordeveloping rectangular timing pulses having a frequency which isproportional to and synchronized with the rotating speed of thecrankshaft 16. The rectangular timing pulses are applied to a timingline 82. Preferably, the timing pulse generator 80 is some type ofinductive speed transducer coupled with a switching circuit. However,the timing pulse generator 80 may be provided by virtually any suitablepulse producing device such as a multiple contact rotary switch.

An injector drive circuit 84 is connected to the power line 40 and tothe timing line 82. Further, the injector drive circuit 84 is connectedthrough an injection line 86 to the fuel injector 48. The injector drivecircuit 84 is responsive to the timing pulses produced by the timingpulse generator 80 to energize the fuel injector valve 48 insynchronization with the rotating speed or frequency of the crankshaft16 in much the same manner as the ignition circuit 44 energizes thespark plug 30. The time period for which the fuel injector 48 isenergized by the drive circuit 84 is determined by the length orduration of rectangular control pulses pro duced by a modulator orcontrol pulse generator 88 which will be more fully described later. Thecontrol pulses are applied by the control pulse generator 88 to theinjector drive circuit 84 over a control line 90 in synchronization withthe timing pulses produced by the timing pulse generator 80. In otherwords, the injector drive circuit 84 is responsive to the coincidence ofa timing pulse and a control pulse to energize the fuel injector 48 forthe length or duration of the control pulse.

The injector drive circuit 84 may be virtually any amplifier circuitcapable of logically executing the desired coincident pulse operation.However, where additional fuel injectors 48 are provided, it may benecessary that the injector drive circuit 84 also select which one orones of the fuel injectors 48 are to be energized in response to eachrespective timing pulse. As an example, the fuel injectors 48 may bedivided into separate groups which are successively energized inresponse to successive ones of the timing pulses. Conversely, the timingpulses may be applied to operate a counter circuit of a logic circuitwhich individuallyselects the fuel injectors 48 for energization.

The control pulse generator. 88 comprises a control circuit 92 and aswitching circuit 94. The control circuit 92 includes a voltageregulator provided by an N PN junction transistor 96. The collectorelectrode of the transistor 96 is connected directly to a junction 98. Apair of biasing resistors 100 and 102 are connected in series beween thepower line 40 and the junction 98. A clamping switch is provided by anNPN junction transistor 104. The collector electrode of the transistor104 is connected directly to the junction 98. The emitter electrode ofthe transistor 104 is connected directly to the ground line 42. Abiasing resistor 106 is connected between the base electrode of thetransistor 104 and a junction 108.

A control transducer 110 includes an inductor or winding 112 connectedbetween the emitter electrode of the transistor 96 and the ground line42. Further, the control transducer 110 includes a movable magnetizablecore 114 which is inductively coupled with the winding 1 12. The deeperthe core 1 14 is inserted within the winding 112, the greater theinductance L of the winding 112. The movable core 114 is mechanicallyconnected through a suitable linkage 116 with a pressure sensor 118. Thepressure sensor 118 communicates with the intake manifold 20 of theengine downstream from the throttle valve 74 through a suitable conduit120 for monitoring the negative pressure or vacuum within the intakemanifold 20. The pressure sensor 118 moves the core 114 within thewinding 112 to regulate the inductance of the winding 112 in directproportion to the pressure within the intake manifold 20. Therefore, asthe pressure within the manifold increases in response to opening of thethrottle valve 74, the core 114 is inserted deeper within the winding112 to proportionately increase the inductance of the winding 1 12.

A biasing circuit 122 is connected with the base electrode of thetransistor 96. The biasing circuit 122 includes NPN junction transistors124, 126 and 128 and a PNP junction transistor 130. A biasing resistor131 is connected between the base electrode of the transistor 124 and ajunction 132. The emitter electrode of the transistor 124 is connecteddirectly to ground line 42. The collector electrode of the transistor124 is connected together with the base electrode of the transistor 126at a junction 134. A biasing resistor 136 is connected between the powerline 40 and the junction 134. A pair of biasing resistors 138 and 140are connected in series between the power line 40 and the collectorelectrode .of the transistor 126.

The base electrode of the transistor 128 is connected directly to theemitter electrode of the transistor 126. The emitter electrode of thetransistor 128 is connected directly to the ground line 42. A biasingresistor 142 is connected in series with a control diode 144 between ajunction 146 and the collector electrode of the transistor 128. Abiasing resistor 148 is connected in series with a control diode 150between the junction 146 and the collector electrode of the transistor130. A biasing resistor 152 is connected between the base electrode ofthe transistor 130 and a junction 154 located between the biasingresistors 138 and 140. The

emitter electrode of the transistor 130 is connected di- 7 rectly to thepower line 40. The base electrode of the transistor 96 is connecteddirectly to the junction 146.

The switching circuit 94 includes a differential switch 156 includingNPN junction transistors 158, 160 and 162. The emitter electrode of thetransistor 158 is connected directly to the ground line 42. The baseelectrode of the transistor 158 is connected to a junction 164. Acurrent reference diode 166 is connected be- I tween the junction 164and the ground line 42. A biasing resistor 168 is connected between thejunction 164 and the power line 40. The collector electrode of thetransistor 158 is connected to a junction 170 between the emitterelectrodes of the transistors 160 and 162. The base electrode of thetransistor 162 is connected directly to a junction 17. A biasingresistor 174 is connected between the junction 172 and the power line40. Similarly, a biasing resistor 176 is connected between the junction172 and the ground line 42. The base electrode of the transistor 160 isconnected directly to a junction 178 located between the biasingresistors 100 and 102. The collector electrode of the transistor 162 isconnected directly to a junction 180. A biasing resistor 182 isconnected between the junction 180 and the power line 40. The collectorelectrode of the transistor 162 is connected directly to the power line40.

A buffer switch 184 is provided by a PNP junction transistor 186 and anNPN junction transistor 188. A n output switch is provided by an NPNjunction transistor 190. The base electrode of the transistor 186 isconnected directly to the junction 180. The emitter electrode of thetransistor 186 is connected together with the collector electrode of thetransistor 188 directly to the power line 40. The collector electrode ofthe transistor 186 is connected directly to the base electrode of thetransistor 188. A biasing resistor 192 is connected between the emitterelectrode of the transistor 188 and a junction 194. A biasing resistor196 is connected between the junction 194 and the ground line 42. Abiasing resistor 198 is connected between the base electrode of thetransistor 190 and the junction 194. A biasing resistor 200 is connectedbetween the collector electrode of the transistor 190 and the power line40. The emitter electrode of the transistor 190 is connected directly tothe ground line 42.

A trigger pulse former 202 is connected between the timing line 82 andthe junctions 132, 108 and 194 of the control pulse generator 88 fordeveloping negative trigger pulses or voltage spikes in response to therectangular timing pulses produced by the timing pulse generator 80.More specifically, the trigger pulse former 202 provides a trigger pulsein coincidence with the initiation of each of the timing pulses on thetiming line 82. Thus, the trigger pulses have the same frequency as thetiming pulses. The trigger pulse former 202 may be provided by a simpleRC differentiator or any other suitable pulse forming circuit. Together,the trigger pulse former 202 and the timing pulse generator comprise atiming apparatus for producing trigger pulses having a frequencyproportional to the output speed of the engine 10.

Referring to FIGS. 1 and 2, the control circuit 92 produces a controlvoltage K at the junction 178. The amplitude of the control voltage Kvaries in a manner which will be more fully described later. In theswitching circuit 94, the resistors 174 and 176 form a voltage dividernetwork for providing a reference voltage R at the junction 172. Theamplitude of the reference voltage R is substantially constant at areference level V, determined by the ratio of the resistances of theresistors 174 and 176. In the conventional manner, the differentialswitch 156 is operable between first and second states. Moreparticularly, the differential switch 156 shifts the the first statewhen the amplitude of the reference voltage R exceeds the amplitude ofthe control voltage K. Conversely, the differential switch 156 shifts tothe second state when the amplitude of the control voltage K-exceeds theamplitude of the reference voltage R. The transistor 158 combines withthe diode 166 and the resistor 168 to provide a constant current sinkfor the differential switch 156 at the junction 170. 7

Initially, it is assumed that the amplitude of the reference voltage Rexceeds the amplitude of the control voltage K so that the differentialswitch shifts to the first state. In the first state, the transistor 162is rendered fully conductive and the transistor is rendered fullynonconductive. With the transistor 162 turned on, the transistors 186and 188 in the buffer switch 184 are rendered fully conductive throughthe biasing action of the resistor 182 and the transistors 158 and 162.With the buffer transistors 186 and 188 turned on, the clampingtransistor 104 is rendered fully conductive through the biasing actionof the resistors 192, 196 and 106. With the transistor 104 turned on,the junction 98 is effectively connected to the ground line 42 throughthe transistor 104. As a result, the amplitude of the control voltage Kat the junction 178 is effectively clamped at an initial level or alower level V primarily defined by the voltage divider action of theresistors 100 and 102. The lower level V of the control voltage K isbelow the reference level V of the reference voltage R so that thedifferential switch 156 remains in the first state.

Further, with the buffer transistors 186 and 188 turned on, the biasingtransistor 124 is rendered fully conductivethrough the biasing action ofthe resistors 192, 196 and 130. With the transistor 124 turned on, thetransistors 126, 128 and 130 in the biasing circuit 122 are renderedfully nonconductive. Moreover, with the buffer transistors 186 and 188turned on, the output transistor 190 is rendered fully conductivethrough the biasing action of the resistors 192, 196 and 198. With thetransistor 190 turned on, the control line 90 is effectively connectedto the ground line 42 through the transistor 190. Thus, no control pulseC is developed on the timing line 90.

As previously described, the trigger pulse former 202 applies negativetrigger pulses P to the junctions 132, 108 and 194 at a frequencydefined in direct relation to the speed of the engine 10. When a triggerpulse P arrives at the junction 194, it instantaneously renders thetransistor 190 fully nonconductive. With the output transistor 190turned off, the control line 90 is effectively disconnected from theground line 42. Accordingly, a control pulse C is initiated on thecontrol line 90. The voltage level of the control pulse C is primarilydetermined by the supply potential on the power line 40.

Further when a trigger pulse P arrives at the junction 108, itinstantaneously renders the transistor. 104 fully nonconductive. Withthe clamping transistor 104 turned off, the junction 98 is effectivelydisconnected from the ground line 42. Consequently, the amplitude of thecontrol voltage K at the junction 178 jumps from the lower level V, to apeak level or an upper level V,, primarily defined by the supplypotential on the power line 40. The upper level V, of the controlvoltage K is above the reference level V, of the reference voltage R sothat the differential switch 156 shifts to the second state. In thesecond state, the transistor 160 is rendered fully conductive and thetransistor 162 is rendered fully nonconductive. With the transistor 162turned off, the transistors 186 and 188 in the buffer, switch 184 arerendered fully nonconductive through the biasing action of the resistor182. With the buffer transistors 186 and 188 turned off, the outputtransistor 190 is maintained turned off.

The transistor 124 is initially turned off in response to the occurrenceof a trigger pulse P at the junction 132 and is subsequently maintainedturned off while the buffer transistors 186 and 188 are turned off. Withthe transistor 124 turned off, the transistor 126 is rendered fullyconductive through the biasing action of the resistor 136. With thetransistor 126 turned on, the transistor 128 is rendered fullyconductive through the biasing action of the resistors 138 and 140, andthe transistor 130 is rendered fully conductive through the biasingaction of the resistors 138, 140 and 152. With the transistors 128 and130 turned on, the resistors 142 and 148 form a voltage divider networkfor developing an energizing voltage E at the junction 146. Theamplitude of the energizing voltage E is substantially constant at anenergizing level V,. which is primarily defined by the ratio of theresistances of the resistors 142 and 148.

The control transistor 96 operates as an emitterfollower to apply theenergizing voltage E across the winding 112 of the control transducer110. lnresponse to the application of the energizing voltage E acrossthe winding 112, a control current J is developed through the winding112. The magnitude of the control current J linearly increases from abase level or a lower level L, to a reference level or an upper level1,, at a constant rate of change directly proportional to the amplitudeV of the energizing voltage E and inversely proportional to theinductance L of the winding 112. As the magnitude of the control currentJ increases, the effective resistance between the collector electrodeand the emitter electrode of the transistor 96 decreases to maintain theenergizing voltage E substantially constant at the energizing level Vacross the winding 112. Of course, the energizing level V of theenergizing voltage E is slightly reduced by the voltage drop across thebase-emitter junction of the transistor 96. Since the inductance L ofthe winding 112 is directly proportional to the pressure within theintake manifold 20, the rate of change in the magnitude of the controlcurrent J is inversely proportional to the intake pressure of the engine10. That is, as the intake pressure of the engine 10 increases, the rateof change in the magnitude of the control current J decreases.

The control current J which is developed through the winding 112 is alsodrawn through the resistors 100 and 102. Accordingly, the controlvoltage K at the junction 178 linearly decreases from the upper level Vat a constant rate of change defined by the constant rate of change inthe magnitude of the control current J. Thus, the rate of change in theamplitude of the control voltage K is also inversely proportional to thepressure within thetintake manifold 20 in the engine 10. When theamplitude of the control voltage K reaches the reference level V, of thereference voltageR, the differential switch 156 shifts to the firststate to terminate the control pulse C on the control line as previouslydescribed.

It will now be appreciated that the duration of the control pulses C isequal to the time period defined between the departure of the controlvoltage K from the upper level V, and the arrival of the control voltageK at the reference level V,. Since this time period is inverselyproportional to the rate of change in the amplitude of the controlvoltage K, the duration of the control pulses C is a direct linearfunction of the pressure within the intake manifold 20. Hence, as theintake pressure of the engine 10 increases the duration of the controlpulses C increases in a linearly proportional manner. Since the fuelinjector 46 is energized for the duration of the control pulses C, thetotal quantity of fuel applied to the engine 10 is linearly related tothe pressure within the intake manifold 20.

When the differential switch 156 shifts to the first state to terminatethe control pulse C, the transistors 104 and 124 are turned on so thatthe transistor 96 is rendered fully nonconductive. As the transistor 96turns off, the winding 1 12 of the control transducer 1 10 iseffectively open circuited. Consequently, a flyback voltage is developedacross the winding 112. The polarity of the flyback voltage is oppositeto-the polarity of the energizing voltage E so that the flyback voltagetends to maintain the flow of current through the winding 112. However,once the transistor 96 is turned off, the flyback voltage is unable todraw any additional current through the winding 1 12. The diode 150blocks the flow of current from the transistor 130 through the resistor148 and the base-emitter diode of the transistor 96. The flow of currentfrom the transistor 128 through the diode 144, the resistor I42 and thebase-emitter diode of the transistor 96 is blocked by the basecollectordiode of the transistor [28. Similarly, the base-collector diode of thetransistor 96 blocks the flow of current through the transistor 96.Under these conditions, the flyback voltage has a minimum duration whichis primarily defined by eddy currents induced within the magnetizablecore 114.

It will now be appreciated that the present invention provides a simplebut effective technique for regulating the amount of fuel applied to aninternal combustion engine as a linear function of at least one engineoperating parameter. However, it will be understood that the illustratedembodiment of the invention is shown for demostration purposes only.Accordingly, various alterations and modifications may be made to thepreferred embodiment without departing from the spirit and scope of theinvention. Thus, in addition manifold pressure, the duration of thecontrol pulses C may be determined as a function of other engineoperating parameters such as air temperature, output speed, batteryvoltage, etc. This may be accomplished by selectively shifting the levelof the energizing voltage E at the junction 146, the reference voltage Rat the junction 172 or the control voltage K at the junction 178 What isclaimed is:

1. In an internal combustion engine, the combination comprising: meansincluding an inductor having an inductance determined as a linearfunction of an engine operating parameter; means for applying insynchronization with the operation of the engine a control voltagehaving a substantially constant amplitude across the inductor to developthrough the inductor a control current having a linearly varyingmagnitude so that the constant rate of change in the magnitude of thecontrol current is proportional to the inductance of the inductor; andmeans for applying fuel to the engine in an amount determined by therate of change in the magnitude of the control current; whereby thetotal quantity of fuel delivered to the engine is a linear function ofthe engine operating parameter.

2. In an internal combustion engine, the combination comprising: meansincluding an inductor having an inductance determined as a linearfunction of an engine operating parameter; means for applying across theinductor in synchronization with the speed of the engine a controlvoltage having a substantially constant amplitude to develop through theinductor a control current having a linearly varying magnitude whichincreases from a base level to a reference level at a constant rateinversely proportional to the inductance of the inductor; and means forapplying fuel to the engine in an amount directly related to the timeperiod defined between the departure of the control current from thebase level and the arrival of the control current at the referencelevel; whereby the total quantity of fuel delivered to the engine is alinear function of the engine operating parameter.

3. In an internal combustion engine, the combination comprising: meansincluding an inductor having an inductance determined as a linearfunction of at least one engine operating parameter; means including atransistor connected with the inductor in an emitter-followerconfiguration for applying across the inductor in synchronization withthe operation of the engine a control voltage having a substantiallyconstant amplitude to develop through the inductor a control currenthaving a linearly varying magnitude which increases from a base level toa reference level at a constant rate determined as an inverse functionof the inductance of the inductor; and means for applying fuel to theengine in an amount determined in direct relation to the time perioddefined between when the control current departs from the base level andwhen the control current arrives at the reference level; whereby thetotal quantity of fuel delivered to the engine is linearly related tothe engine operating parameter.

4. In an internal combustion engine, the combination comprising: meansincluding an inductor having an inductance determined as a linearfunction of at least one engine operating parameter; means including atleast one resistor having a fixed resistance; means including a junctiontransistor connected in an emitter-follower configuration between theinductor and the resistor to apply across the inductor insynchronization with the operation of the engine a control voltagehaving a substantiallyconstant amplitude to generate through theinductor and through the resistor a control current having a linearlyvarying magnitude to develop across the resistor a control voltagehaving a linearly varying amplitude which decreases from a peak level toa reference level at a rate inversely proportional to the inductance ofthe inductor; and means for applying fuel to the engine in an amountdefined by the time period extending between the departure of thecontrol voltage from the peak level and the arrival of the controlvoltage at the reference level; whereby the total quantity of fueldelivered to the engine is linearly related to the engine operatingparameter.

5. In an internal combustion engine, the combination comprising: meansincluding a junction transistor having base, emitter and collectorelectrodes; means connected to the emitter electrode of the transistorand including an inductor having an inductance determined as a'linearfunction of at least one engine operating parameter; means connectedwith the collector electrode of the transistor and including at leastone resistor having' a resistance which is substantially constant; meansconnected to the base electrode of the transistor for periodicallyoperating the transistor as an emitterfollower in synchronization withthe operation of the engine to apply across the inductor a controlvoltage having an amplitude which is substantially constant to generatethrough the inductor and through the resistor a control current having amagnitude which linearly increases to develop across the resistor acontrol voltage having an amplitude which linearly decreases from a peaklevel to a reference level at a constant rate inversely proportional tothe inductance of the inductor; and means for applying fuel to theengine in an amount directly related to the time period extendingbetween the departure of the control voltage from the peak level and thearrival of the control voltage at the reference level; whereby the totalquantity of fuel delivered to the engine is a linear function of theengine operating parameter.

6. In an internal combustion engine, the combination comprising: meansincluding a timing generator connected with the engine for producingtrigger pulses occurring at a frequency proportional to the speed of theengine; means including a junction transistor having base, emitter andcollector electrodes; means connected to the emitter electrode of thetransistor and including an inductor having an inductance determined asa linear function of at least one engine operating parameter; meansconnected to the collector electrode of the transistor and including atleast one resistor having a resistance which is substantially constant;means connected to the base electrode of the transistor and to thetiming generator for periodically rendering the transistor conductive inan emitter-follower configuration in response to the occurrence of eachtrigger pulse to apply across the inductor a control voltage having anamplitude which is substantially constant to develop through theinductor and through the resistor a control current having a magnitudewhich linearly increases to generate across the resistor a controlvoltage having an amplitude which linearly decreases from a peak levelto a reference level at a constant rate determined in proportion to theinductance of the inductor; means including a differential switch forshifting from a first state to a second state when the control voltagereaches the reference level; means connected to the timing generator andto the differential switch for producing a control pulse which isinitiated in response to the occurrence of each trigger pulse and whichis terminated when the differential switch shifts to the second state;and means for applying fuel to the engine at a constant rate for theduration of the control pulse; whereby the total quantity of fueldelivered to the engine is a linear function of the engine operatingparameter.

UNITED STATES PATENT O FFICE 7 CERTIFICATE OF CORRECTION Patent No.3,774,580 Dated November 27, 1973 Inventor Lil-.1511 P McGavic It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

' Column'B, line 20 "th" should read the Column 5, line 57 "17 shouldread 172. Column 6, line 49 "the the" should read tothe si ed and sealedthis 30th day of July 197 (SEAL) Attest:

MCCOY M. GIBSON, JR; H c. MARSHALL DANN Attesting Officer Commissionerof Patents

1. In an internal combustion engine, the combination comprising: meansincluding an inductor having an inductance determined as a linearfunction of an engine operating parameter; means for applying insynchronization with the operation of the engine a control voltagehaving a substantially constant amplitude across the inductor to developthrough the inductor a control current having a linearly varyingmagnitude so that the constant rate of change in the magnitude of thecontrol current is proportional to the inductance of the inductor; andmeans for applying fuel to the engine in an amount determined by therate of change in the magnitude of the control current; whereby thetotal quantity of fuel delivered to the engine is a linear function ofthe engine operating parameter.
 2. In an internal combustion engine, thecombination comprising: means including an inductor having an inductancedetermined as a linear function of an engine operating parameter; meansfor applying across the inductor in synchronization with the speed ofthe engine a control voltage having a substantially constant amplitudeto develop through the inductor a control current having a linearlyvarying magnitude which increases from a base level to a reference levelat a constant rate inversely proportional to the inductance of theinductor; and means for applying fuel to the engine in an amountdirectly related to the time period defined between the departure of thecontrol current from the base level and the arrival of the controlcurrent at the reference level; whereby the total quantity of fueldelivered to the engine is a linear function of the engine operatingparameter.
 3. In an internal combustion engine, the combinationcomprising: means including an inductor having an inductance determinedas a linear function of at least one engine operating parameter; meansincluding a transistor connected with the inductor in anemitter-follower configuration for applying across the inductor insynchronization with the operation of the engine a control voltagehaving a substantially constant amplitude to develop through theinductor a control current having a linearly varying magnitude whichincreases from a base level to a reference level at a constant ratedetermined as an inverse function of the inductance of the inductor; andmeans for applying fuel to the engine in an amount determined in directrelation to the time period defined between when the control currentdeparts from the base level and when the control current arrives at thereference level; whereby the total quantity of fuel delivered to theengine is linearly related to the engine operating parameter.
 4. In aninternal combustion engine, the combination comprising: means includingan inductor having an inductance determined as a linear function of atleast one engine operating parameter; means including at least oneresistor having a fixed resistance; means including a junctiontransistor connected in an emitter-follower configuration between theinductor and the resistor to apply across the inductor insynchronization with the operation of the engine a control voltagehaving a substantially constant amplitude to generate through theinductor and through the resistor a control current having a linearlyvarying magnitude to develop across the resistor a control voltagehaving a linearly varying amplitude which decreases from a peak level toa reference level at a rate inversely proportional to the inductance ofthe inductor; and means for applying fuel to the engine in an amountdefined by the time period extending between the departure of thecontrol voltage from the peak level and the arrival of the controlvoltage at the reference level; whereby the total quantity of fueldelivered to the engine is linearly related to the engine operatingparameter.
 5. In an internal combustion engine, the combinationcomprising: means including a junction transistor having base, emitterand collector electrodes; means connected to the emitter electrode ofthe transistor and including an inductor having an inductance determinedas a linear function of at least one engine operating parameter; meansconnected with the collector electrode of the transistor and includingat least one resistor having a resistance which is substantiallyconstant; means conNected to the base electrode of the transistor forperiodically operating the transistor as an emitter-follower insynchronization with the operation of the engine to apply across theinductor a control voltage having an amplitude which is substantiallyconstant to generate through the inductor and through the resistor acontrol current having a magnitude which linearly increases to developacross the resistor a control voltage having an amplitude which linearlydecreases from a peak level to a reference level at a constant rateinversely proportional to the inductance of the inductor; and means forapplying fuel to the engine in an amount directly related to the timeperiod extending between the departure of the control voltage from thepeak level and the arrival of the control voltage at the referencelevel; whereby the total quantity of fuel delivered to the engine is alinear function of the engine operating parameter.
 6. In an internalcombustion engine, the combination comprising: means including a timinggenerator connected with the engine for producing trigger pulsesoccurring at a frequency proportional to the speed of the engine; meansincluding a junction transistor having base, emitter and collectorelectrodes; means connected to the emitter electrode of the transistorand including an inductor having an inductance determined as a linearfunction of at least one engine operating parameter; means connected tothe collector electrode of the transistor and including at least oneresistor having a resistance which is substantially constant; meansconnected to the base electrode of the transistor and to the timinggenerator for periodically rendering the transistor conductive in anemitter-follower configuration in response to the occurrence of eachtrigger pulse to apply across the inductor a control voltage having anamplitude which is substantially constant to develop through theinductor and through the resistor a control current having a magnitudewhich linearly increases to generate across the resistor a controlvoltage having an amplitude which linearly decreases from a peak levelto a reference level at a constant rate determined in proportion to theinductance of the inductor; means including a differential switch forshifting from a first state to a second state when the control voltagereaches the reference level; means connected to the timing generator andto the differential switch for producing a control pulse which isinitiated in response to the occurrence of each trigger pulse and whichis terminated when the differential switch shifts to the second state;and means for applying fuel to the engine at a constant rate for theduration of the control pulse; whereby the total quantity of fueldelivered to the engine is a linear function of the engine operatingparameter.